1. Field of the Disclosure
The present disclosure relates to an apparatus to measure bio-information. Particularly, the present disclosure relates to an apparatus to measure bio-information regarding human heartbeats, such as cardiac potential and pulse waves, and more specifically, to a neck-band type bio-information detecting apparatus attached around a human neck part.
2. Description of Related Art
There have been developed techniques of promoting reduction in dimension of sensors capable of measuring bio-information regarding human heartbeats, such as cardiac potential and pulse waves, and transmitting measurement values of these sensors via radio communication. Therefore, there have been proposed various portable bio-information detecting apparatuses attached to heads, necks, or the like of examinees so as to allow the examinees to relatively freely take exercise. For example, in Japanese Patent Application Publication No. 2003-325466, proposed is a bio-information detecting apparatus configured to include electrodes coming into contact with a neck part of an examinee so as to detect cardiac potential of the examinee, at both ends of a C-shaped neck band attached to the examinee from the back side of his or her neck part, and transmit the potential difference of the electrodes to the outside via radio communication. Japanese Patent Application Publication No. 2007-202939 discloses a configuration that provides both ends of a C-shaped neck band as described above with not only measurement means of cardiac potential, but also sensor means to optically measure blood oxygen saturation in the carotid artery of an examinee so as to detect his or her pulse waves. Furthermore, Japanese Patent Application Publication No. 2015-73557 discloses a configuration that provides a C-shaped neck band attached to an examinee from the back side of his or her neck part with sensor means to optically measure blood oxygen saturation, in particular, a bio-information detecting apparatus configured to include cardiac potential measurement means and pulse wave detecting means to optically measure blood oxygen saturation on a C-shaped neck band of the apparatus attached from the back side of a neck part has an advantage in that the apparatus has a smaller dimension, and does not cause much influence on any exercise taken by an examinee.
One of current challenges in bio-information detecting apparatuses including measurement means to measure cardiac potential and pulse waves on neck bands attached around neck parts is to measure cardiac potential and blood oxygen saturation with as high measurement sensitivity as possible. For example, if cardiac potential is measured at a neck part, its measurement part is located apart from a heart; thus measurement sensitivity becomes considerably deteriorated compared with the case of measuring cardiac potential at a chest part near the heart. Actually, cardiac potential measuring means of a type that has electrodes at both ends of a neck band detects considerably smaller amplitudes of measurement values of cardiac potential. When a neck band is attached around a neck part, elasticity of the neck band is utilized so as to prevent the neck band from dropping off the neck. However, depending on the degree of pressure onto a vessel with too strong elasticity, it is confirmed that some influence might be caused to amplitudes of measurement values of pulse waves (blood oxygen saturation). Hence, in above described neck-band type bio-information detecting apparatuses attached around neck parts, it is preferable to improve configurations thereof in order to improve measurement sensitivity of cardiac potential and pulse waves.